# Monthly Archives: April 2014

## An Assembly program to conduct a binary search on a given sorted array of 16-bit, unsigned integers, and a given 16-bit unsigned key

Now we will write another Assembly program to conduct a binary search on a given sorted array of 16-bit, unsigned integers, and a given 16-bit unsigned key.

The above Logic is a C like Program to conduct a binary search we need small Algorithm Shown above in a very simple way, So Just we will covert the logic into Assembly There are many things uncommon in the programing Language. There are No While Loops or Modules but this things are to be implemented in different ways.

Let’s identify variables needed for this program.
First variables will be the one which will hold the values present in the Given Numbers in Array list and key of 16-bit and it will be array ARR and KEY. variables will be holding the Messages MSG1 “KEY IS FOUND AT “, RES “  POSITION”, 13, 10,” \$” and MSG2 ‘KEY NOT FOUND!!!.\$’ to be printed for the User. Other variables will be holding Length of the Array and it will be LEN, So in all Six variables.
The identified variables are ARR, KEY, LEN, RES, MSG1 and MSG2.

First Line – DATA SEGMENT

DATA SEGMENT is the starting point of the Data Segment in a Program and DATA is the name given to this segment and SEGMENT is the keyword for defining Segments, Where we can declare our variables.

Next Line – ARR DW 0000H,1111H,2222H,3333H,4444H,5555H,6666H,7777H,8888H,9999H
LEN DW (\$-ARR)/2
KEY EQU 7777H
MSG1 DB “KEY IS FOUND AT ”
RES DB “  POSITION”,13,10,” \$”

ARR DW 0000H,1111H,2222H,3333H,4444H,5555H,6666H,7777H,8888H,9999H this line is a declaration of 16-bit Numbers Array initialized with 0000H,1111H,2222H,3333H,4444H,5555H,6666H,7777H,8888H,9999H the numbers are seperated by Comma (,). LEN DW \$-ARR is used to Save the Length of the Array which will be generated by \$-Name of the array i.e. \$-ARR. KEY EQU 7777H is used to save given KEY to be Searched in the Array and is equal to (EQU) 7777H. MSG1 DB “KEY IS FOUND AT ” this line is a declaration of Charater Array initialized with “KEY IS FOUND AT”. (A Character is of a BYTE Hence we have to use only DB Define Byte ) and Similarly to RES and MSG2.  Detailed explanation is given below.

Next Line – DATA ENDS

DATA ENDS is the End point of the Data Segment in a Program. We can write just ENDS But to differentiate the end of which segment it is of which we have to write the same name given to the Data Segment.

Now, Selection of data type is DW data type the numbers which we are adding is 16-bit  integers so DW is sufficient.

 Source code
```DATA SEGMENT
ARR DW 0000H,1111H,2222H,3333H,4444H,5555H,6666H,7777H,8888H,9999H
LEN DW (\$-ARR)/2
KEY EQU 7777H
MSG1 DB "KEY IS FOUND AT "
RES DB "  POSITION",13,10," \$"
DATA ENDS```

In Assembly programming, the variable are all defined by bytes only.

DB – Define Byte  (Size – 1 Byte)

DW – Define Word  (Size – 2 Byte)

DD – Define Double word  (Size -  4 Bytes)

DQ – Define Quad word  (Size – 8 Bytes)

DT – Define Ten Bytes  (Size – 10 Bytes)

NUMBER SYSTEM in Assembly Programming is Decimal, Octal, Hexadecimal, Binary.

In the Program, We are entering the values for the variables and Do arithmetical Operations like Addition, Subtraction, Multiplication and Division So the Computer should understand which kind of Number is entered. Hence there is a different letters for different Number Systems. O or o stands for Octal, H or h stands for Hexadecimal, B or b stands for Binary, D or d stands for Decimal. By default type of numbering system is Decimal. If you do not specify any letter then the number is understood to be Decimal (By default).

 Source code
```DATA SEGMENT
ARR DW 0000H,1111H,2222H,3333H,4444H,5555H,6666H,7777H,8888H,9999H
LEN DW (\$-ARR)/2
KEY EQU 7777H
MSG1 DB "KEY IS FOUND AT "
RES DB "  POSITION",13,10," \$"
DATA ENDS
CODE SEGMENT
ASSUME DS:DATA CS:CODE
START:
MOV AX,DATA
MOV DS,AX

MOV BX,00
MOV DX,LEN
MOV CX,KEY
AGAIN: CMP BX,DX
JA FAIL
MOV AX,BX
SHR AX,1
MOV SI,AX
CMP CX,ARR[SI]
JAE BIG
DEC AX
MOV DX,AX
JMP AGAIN
BIG:   JE SUCCESS
INC AX
MOV BX,AX
JMP AGAIN
MOV RES,AL
LEA DX,MSG1
JMP DISP
FAIL: LEA DX,MSG2
DISP: MOV AH,09H
INT 21H

MOV AH,4CH
INT 21H
CODE ENDS
END START```

Explanation :

In this Assembly Language Programming, A single program is divided into four Segments which are 1. Data Segment, 2. Code Segment, 3. Stack Segment, and 4. Extra  Segment. Now, from these one is compulsory i.e. Code Segment if at all you don’t need variable(s) for your program.if you need variable(s) for your program you will need two Segments i.e. Code Segment and Data Segment.

Next Line – CODE SEGMENT

CODE SEGMENT is the starting point of the Code Segment in a Program and CODE is the name given to this segment and SEGMENT is the keyword for defining Segments, Where we can write the coding of the program.

Next Line –     ASSUME DS:DATA CS:CODE

In this Assembly Language Programming, their are Different Registers present for Different Purpose So we have to assume DATA is the name given to Data Segment register and CODE is the name given to Code Segment register (SS,ES are used in the same way as CS,DS )

Next Line – START:

START is the label used to show the starting point of the code which is written in the Code Segment. : is used to define a label as in C programming.

Next Line – MOV AX,DATA
MOV DS,AX

After Assuming DATA and CODE Segment, Still it is compulsory to initialize Data Segment to DS register.  MOV is a keyword to move the second element into the first element. But we cannot move DATA Directly to DS due to MOV commands restriction, Hence we move DATA to AX and then from AX to DS. AX is the first and most important register in the ALU unit. This part is also called INITIALIZATION OF DATA SEGMENT and It is important so that the Data elements or variables in the DATA Segment are made accessable. Other Segments are not needed to be initialized, Only assuming is enhalf.

Next Line – MOV BX,00
MOV DX,LEN
MOV CX,KEY

The above two line of code is same as FIRST=0 and LAST=LEN the Difference is that we are using Registers to Store Numbers, So we have t0 instruction MOV BX,00 move ZERO value to BX Register.  MOV DX,LEN move LEN variable value to DX Register. MOV CX,KEY move KEY variable value to CX Register.

Next Line – AGAIN: CMP BX,DX
JA FAIL

AGAIN: this will be starting point of while loop the condition cannot be written here So we write it Down and this is a LABEL and all the words ending in colon (:). CMP BX,DX is used to compare Element of BX register with DX register and JA FAIL Short Jump if first operand (i.e. BX) is Above second operand (i.e. DX) to the respective LABEL FAIL. The result of Comparision is not stored anywhere, but flags are set according to result.

Next Line – MOV AX,BX
SHR AX,1
MOV SI,AX

MOV BX,CX is to move CX register to BX register. ADD AX,DX means Adding value of DX register with AX register. SHR means Shift operand1 Right. The number of shifts is set by operand2. SHR AX,1 is used to Shift with 1. MOV SI,AX is to move AX register to SI register. ADD SI,SI means Adding value of SI register with SI register.

Next Line – CMP CX,ARR[SI]
JAE BIG
DEC AX
MOV DX,AX
JMP AGAIN

CMP CX,ARR[SI] is used to compare Element of CX register with Element of Array present in ARR[SI] and JAE BIG Short Jump if first operand (i.e. BX) is Above or Equal to second operand (i.e. DX) to the respective LABEL BIG. The result of Comparision is not stored anywhere, but flags are set according to result. DEC AX will decrement the Address value present in AX register. MOV DX,AX is to move AX register to DX register. JMP AGAIN is used to Jump to Label AGAIN without any condition check. This jump will basically Continue the Loop execution.

Next Line –BIG:   JE SUCCESS
INC AX
MOV BX,AX
JMP AGAIN

BIG: is a LABEL and all the words ending in colon (:). JE SUCCESS Short Jump if first operand (i.e. BX) is Equal to second operand (i.e. DX) to the respective LABEL SUCCESS. The result of Comparision is not stored anywhere, but flags are set according to result. INC AX will increment the Address value present in AX register. MOV BX,AX is to move AX register to BX register. JMP AGAIN is used to Jump to Label AGAIN without any condition check. This jump will basically Continue the Loop execution.

Next Line – SUCCESS: ADD AL,01
MOV RES,AL
LEA DX,MSG1
JMP DISP

SUCCESS: is a LABEL and all the words ending in colon (:). ADD AL,01 means Adding value 01 to AL register. ADD AL,’0′ means Adding value of ’0′ (i.e. 30H) with AL register. MOV RES,AL is to move AL register to RES variable. LEA DX,MSG1  in this LEA stands for LOAD EFFECTIVE ADDRESS and it loads the effective address of second element into the first element. JMP DISP is used to Jump to Label DISP without any condition check. This jump will basically Continue the Loop execution.

Next Line – FAIL: LEA DX,MSG2

FAIL: is a LABEL and all the words ending in colon (:). LEA DX,MSG2  in this LEA stands for LOAD EFFECTIVE ADDRESS and it loads the effective address of second element into the first element.

Next Line – DISP: MOV AH,09H
INT 21H

DISP: is a LABEL and all the words ending in colon (:). MOV AH,09H  INT 21H is used to PRINT the String or Message of the address present in DX register.

Next Line – MOV AH,4CH
INT 21H

The above two line code is used to exit to dos or exit to operating system. Standard Input and Standard Output related Interupts are found in INT 21H which is also called as DOS interrupt. It works with the value of AH register, If the Value is 4ch, That means Return to Operating System or DOS which is the End of the program.

Next Line – CODE ENDS

CODE ENDS is the End point of the Code Segment in a Program. We can write just ENDS But to differentiate the end of which segment it is of which we have to write the same name given to the Code Segment.

Last Line – END START

END START is the end of the label used to show the ending point of the code which is written in the Code Segment.

Note :- In this Assembly Language Programming, We have Com format and EXE format. We are Learning in EXE format only which simple then COM format to understand and Write. We can write the program in lower or upper case, But i prepare Upper Case.

Screen Shots :-

Output After Execution :-

Note :- To see the variable and its value you have to click vars button in the emulator.

## An Assembly program which should convert 4 digits BCD number into its binary equivalent

Now we will write another Assembly which should convert 4 digits BCD number into its binary equivalent.

Let’s identify variables needed for this program.
First variables will be the one which will hold the value present in the variable BCD to be converted and TEMP will hold the converted Hexadecimal equivalent and then to print its Binary form on Console (Screen) and Other variable RES will be holding the Resultant Binary equivalent printable form to be printed for the User on Screen, So in all  Three variables.
The identified variables are BCD, TEMP and RES.

First Line – DATA SEGMENT

DATA SEGMENT is the starting point of the Data Segment in a Program and DATA is the name given to this segment and SEGMENT is the keyword for defining Segments, Where we can declare our variables.

Next Line – BCD DW 1234H
TEMP DB ?
RES  DB 17 DUP (‘\$’)

BCD DW 1234H We are initializing BCD to 1234H  (H stands for Hexadecimal value). TEMP DB ?  We are initializing to ? (? stands for blank value), As we will save converted BCD form number to Hexadecimal equivalent in it. RES  DB 10 DUP (‘\$’) this line is a declaration of Array initialized with ’\$’ which works as New Line Character. \$ is used as (\n) NULL character in C program. (A Number Character is of a BYTE size Hence we have to used only DB Define Byte ) as we don’t know the lenght of the digits in the Resultant Decimal equivalent printable form, Therefore we take it approx size ten. Here 10 DUP (‘\$’) stands for N i.e. Size of Array or Array Size. DUP stands for Duplicate i.e. it will duplicate the value in All the Array with the value present in Bracket (i.e. \$).

Next Line – DATA ENDS

DATA ENDS is the End point of the Data Segment in a Program. We can write just ENDS But to differentiate the end of which segment it is of which we have to write the same name given to the Data Segment.

Now, Selection of data type is DB data type the numbers which we are adding will be integers so DB is sufficient.

 Source code
```DATA SEGMENT
BCD DW 1234H
TEMP DB ?
RES  DB 17 DUP ('\$')
DATA ENDS```

In Assembly programming, the variable are all defined by bytes only.

DB – Define Byte  (Size – 1 Byte)

DW – Define Word  (Size – 2 Byte)

DD – Define Double word  (Size -  4 Bytes)

DQ – Define Quad word  (Size – 8 Bytes)

DT – Define Ten Bytes  (Size – 10 Bytes)

NUMBER SYSTEM in Assembly Programming is Decimal, Octal, Hexadecimal, Binary.

In the Program, We are entering the values for the variables and Do arithmetical Operations like Addition, Subtraction, Multiplication and Division So the Computer should understand which kind of Number is entered. Hence there is a different letters for different Number Systems. O or o stands for Octal, H or h stands for Hexadecimal, B or b stands for Binary, D or d stands for Decimal. By default type of numbering system is Decimal. If you do not specify any letter then the number is understood to be Decimal (By default).

 Source code
```DATA SEGMENT
BCD DW 1234H
TEMP DB ?
RES  DB 17 DUP ('\$')
DATA ENDS
CODE SEGMENT
ASSUME DS:DATA,CS:CODE
START:
MOV AX,DATA
MOV DS,AX

MOV AX,BCD
MOV BL,AL

AND AL,0F0H
AND BL,0FH

MOV CL,04H
ROL AL,CL

MOV CL,10
MUL CL

MOV TEMP,AL

MOV AX,BCD
MOV AL,AH
MOV AH,0
MOV BL,AL

AND AL,0F0H
AND BL,0FH

MOV CL,04H
ROL AL,CL

MOV CL,10
MUL CL

MOV CL,100
MUL CL

MOV BL,TEMP
MOV BH,0

LEA SI,RES
CALL HEX2BIN

LEA DX,RES
MOV AH,9
INT 21H

MOV AH,4CH
INT 21H
CODE ENDS
HEX2BIN PROC NEAR
MOV CX,0
MOV BX,2

LOOP1: MOV DX,0
DIV BX
PUSH DX
INC CX
CMP AX,1
JG LOOP1

MOV [SI],AL

LOOP2: POP AX
INC SI
MOV [SI],AL
LOOP LOOP2
RET
HEX2BIN ENDP

END START```

Explanation :

In this Assembly Language Programming, A single program is divided into four Segments which are 1. Data Segment, 2. Code Segment, 3. Stack Segment, and 4. Extra  Segment. Now, from these one is compulsory i.e. Code Segment if at all you don’t need variable(s) for your program.if you need variable(s) for your program you will need two Segments i.e. Code Segment and Data Segment.

Next Line –CODE SEGMENT

CODE SEGMENT is the starting point of the Code Segment in a Program and CODE is the name given to this segment and SEGMENT is the keyword for defining Segments, Where we can write the coding of the program.

Next Line –     ASSUME DS:DATA CS:CODE

In this Assembly Language Programming, their are Different Registers present for Different Purpose So we have to assume DATA is the name given to Data Segment register and CODE is the name given to Code Segment register (SS,ES are used in the same way as CS,DS )

Next Line – START:

START is the label used to show the starting point of the code which is written in the Code Segment. : is used to define a label as in C programming.

Next Line – MOV AX,DATA
MOV DS,AX

After Assuming DATA and CODE Segment, Still it is compulsory to initialize Data Segment to DS register.  MOV is a keyword to move the second element into the first element. But we cannot move DATA Directly to DS due to MOV commands restriction, Hence we move DATA to AX and then from AX to DS. AX is the first and most important register in the ALU unit. This part is also called INITIALIZATION OF DATA SEGMENT and It is important so that the Data elements or variables in the DATA Segment are made accessable. Other Segments are not needed to be initialized, Only assuming is enhalf.

Next Line – MOV AX,BCD
MOV BL,AL

MOV AX,BCD is used to Move  BCD variable value to AX Register.  MOV BL,AL to Move  BL Register to AL Register.

Next Line – AND AL,0F0H
AND BL,0FH

The above line code is used to Mask Left and Right Digits in AL Register and BL Register.

Next Line –     MOV CL,04H
ROL AL,CL

ROL means Rotate operand1 left. The number of rotates is set by operand2. We need 4 digits to be Rotated Hence MOV CL,04H is used to Move  04H to CL Register. ROL AL,CL is used to Rotate AL Register to 4 digits Left.

Next Line – MOV CL,10
MUL CL

MUL 10 is not possible where 10 is immediate, So we have to move 10 to CL register (we can take any register) i.e. MOV CL,10. MUL CL in this line CL register will be Multiplied with AX register (BY DEFAULT).

MOV TEMP,AL

ADD AL,BL means Adding value of AL register with BL register. MOV TEMP,AL is used to Move AL Register to TEMP variable.

Next Line – MOV AX,BCD
MOV AL,AH
MOV AH,0
MOV BL,AL

MOV AX,BCD is used to Move  BCD variable value to AX Register. MOV AL,AH to Move  AL Register to AH Register. MOV AH,0 is used to clear the unwanted value (garbage value) in AH register is removed by assigning ZERO to it. MOV BL,AL to Move  BL Register to AL Register.

Next Line – AND AL,0F0H
AND BL,0FH

The above line code is used to Mask Left and Right Digits in AL Register and BL Register.

Next Line –     MOV CL,04H
ROL AL,CL

ROL means Rotate operand1 left. The number of rotates is set by operand2. We need 4 digits to be Rotated Hence MOV CL,04H is used to Move  04H to CL Register. ROL AL,CL is used to Rotate AL Register to 4 digits Left.

Next Line – MOV CL,10
MUL CL

MUL 10 is not possible where 10 is immediate, So we have to move 10 to CL register (we can take any register) i.e. MOV CL,10. MUL CL in this line CL register will be Multiplied with AX register (BY DEFAULT).

Next Line – MOV CL,100
MUL CL

MUL 10 is not possible where 10 is immediate, So we have to move 10 to CL register (we can take any register) i.e. MOV CL,100. MUL CL in this line CL register will be Multiplied with AX register (BY DEFAULT).

Next Line – MOV BL,TEMP

MOV BL,TEMP is used to Move TEMP variable to BL Register.

Next Line – MOV BH,0

MOV BH,0 is used to clear the unwanted value (garbage value) in BH register is removed by assigning ZERO to it.

Next Line – LEA SI,RES
CALL HEX2BIN

The above Two line code is used to initialize RES to SI register and Call Procedure HEX2BIN

LEA SI,RES is used to Load Effective Address of RES variable to SI Register.

CALL HEX2BIN is used to Call a Procedure named HEX2BIN

Next Line – LEA DX,RES
MOV AH,9
INT 21H

The above three line code is used to print String or Message present in the character Array till \$  symbol which tells the compiler to stop. As we have initialized all the values in an Array to \$ you will think what will be printed. The procedure is going to change the Array to its Resultant Decimal equivalent printable form i.e. ASCII form of a digit number.

Now, lets understand line by line

LEA DX,RES in this LEA stands for LOAD EFFECTIVE ADDRESS and it loads the effective address of second element into the first element.  This same code can be interchangably written as MOV DX, OFFSET RES where OFFSET  means effective address and MOV means move  second element into the first element.

MOV AH,9
INT 21H

The above two line code is used to PRINT the String or Message of the address present in DX register.

Standard Input and Standard Output related Interupts are found in INT 21H which is also called as DOS interrupt. It works with the value of AH register, If the Value is 9 or 9h, That means PRINT the String or Message of the address present in DX register.

Next Line – EXIT: MOV AH,4CH
INT 21H

The above two line code is used to exit to dos or exit to operating system. Standard Input and Standard Output related Interupts are found in INT 21H which is also called as DOS interrupt. It works with the value of AH register, If the Value is 4ch, That means Return to Operating System or DOS which is the End of the program.

Next Line – CODE ENDS

CODE ENDS is the End point of the Code Segment in a Program. We can write just ENDS But to differentiate the end of which segment it is of which we have to write the same name given to the Code Segment.

PROCEDURE Code starts here:

Procedure is a part of code that can be called from a program in order to perform specific task.

Next Line – HEX2BIN PROC NEAR

This line of code is used to start a procedure code and we can make out the procedure by the keyword PROC which tells us the procedure is started. In assembly language we have two types of Procedures one is NEAR and other is FAR. NEAR is used to call the Procedure within the program whereas FAR is used to call the procedure outside the program. HEX2BIN is only the Name given to the Procedure Code.

Next Line –  MOV CX,0
MOV BX,2

MOV CX,0 is used to move or assign value 0 (decimal value) to  CX. The program which we are wishing to write is to covert HexaDecimal value to Decimal value, In which we will divide the number till the Quotient is going to be Zero. CX register ( CX is also Called COUNTER). CX register will count the number digit generated by dividing the Hexadecimal number by Base value of Decimal i.e.Ten. MOV BX,2 in this Base value 10 is moved to BX register, So that it is used to divide hexa number by 10.

Next Line – LOOP1: MOV DX,0

LOOP1: is a LABEL and all the words ending in colon (:) are Labels. MOV DX,0 is used to clear the unwanted value (garbage value) in DX register is removed by assigning ZERO to it. First Loop starts here.

Next Line – DIV BX

DIV instruction only works with REG or MEMORY hence we cannot use DIV 10 where 10 is immediate, So we have to move 10 to BX register (we can take any register) this we have already done above and Then DIV BX  Now DIV BX will Divide AX register with 10 which is passed to BX register and Result of division is present in AX register contains Quotientand DX register contains Remainder. Here we will not touch Quotient AX as it will be used for furture Division, But DX Remainder will be Decimal Digit and will always be less than Ten so the value will be in DL register only and to make it printable on Console (Screen) we have to add  30H So that it will become a ASCII character and will be saved in Charater Array and will be printed as String later So ADD DL,30H.

Next Line – PUSH DX
INC CX

PUSH is a stack function. Stack is an area of memory for keeping temporary data. PUSH and POP are two stack operations which stores or gets 16 bits of data. PUSH DX stores 16 bit data inside DX register into Stack Area. INC is a instruction for Increment the present in Register or Memory. INC CX will increment the value present in CX register by One. Here we are using CX register as a counter and counting the numbers of digits in their ASCII form which are pushed into Stack. So that the same count will help to POP the values out of Stack.

Next Line – CMP AX,1
JG LOOP1

CMP AX,9  is used to compare AX register with 9 and jump if AX is greater to the respective LABEL LOOP1. The result of Comparision is not stored anywhere, but flags are set according to result.  is Short Jump if first operand is Greater then second operand (as set by CMP instruction). Signed. SECOND is the label where the compiler will JUMP. First Loop ends here. Note :- this loop is without LOOP keyword and depends upon the number to be converted.

MOV [SI],AL

ADD AL,30H The Last Remainder will be Decimal Digit in AX register only as the number cannot be divided future and will always be less than Ten so the value will be in AL register only and to make it printable on Console (Screen) we have to add  30H So that it will become a ASCII character and will be saved in Charater Array and will be printed as String later. MOV [SI],AL Saving the Characters in Character Array (i.e. String) is done by Moving AL register to Address of SI register which is represented in Square Brackets i.e. [SI]. SI is assigned with the Character Array i.e. RES.

Next Line – LOOP2: POP AX
INC SI

LOOP2: is a LABEL and all the words ending in colon (:) are Labels. POP is a stack function. Stack is an area of memory for keeping temporary data. PUSH and POP are two stack operations which stores or gets 16 bits of data. POP AX gets 16 bit data to AX register from Top of Stack. INC CX will increment the value present in CX register by One. Here we are using CX register as a counter and counting the numbers of digits in their ASCII form which are pushed into Stack. So that the same count will help to POP the values out of Stack and save it in AX register. Second Loop starts here.

Next Line – MOV [SI],AL

The values out of Stack saved in AX register saved in string in this Loop. MOV [SI],AL Saving the Characters in Character Array (i.e. String) is done by Moving AL register to Address of SI register which is represented in Square Brackets i.e. [SI]. SI is assigned with the Character Array i.e. RES.

Next Line – LOOP LOOP2

This end of loop. In assembly programming language we have a LOOP instruction. This works with two other helpers which are Label and Counter. The Loop start with LABEL and ends with LOOP instruction with the same LABEL name with it. the execution of the Loop depends on the value in CX register ( CX is also Called COUNTER).

Next Line – RET

RET is a return instruction. This instruction is used only if  the control is been passed to the code outside Main like to Procedure. this return the control to the place where the Procudure was called.

Next Line – HEX2BIN ENDP

HEX2BIN ENDP is the End point of the Procedure in a Program.

This line of code is used to end the procedure code and we can make out the procedure by the keyword ENDP which tells us the procedure is ended. In assembly language we have two types of Procedures one is NEAR and other is FAR. NEAR is used to call the Procedure within the program whereas FAR is used to call the procedure outside the program. HEX2BIN is only the Name given to the Procedure Code.

Last Line – END START

END START is the end of the label used to show the ending point of the code which is written in the Code Segment.

Note :- In this Assembly Language Programming, We have Com format and EXE format. We are Learning in EXE format only which simple then COM format to understand and Write. We can write the program in lower or upper case, But i prepare Upper Case.

Screen Shots :-

Output After Execution :-

Note :- To see the variable and its value you have to click vars button in the emulator.

## An Assembly Program, which should add two 5-byte numbers (numbers are stored in array- NUM1 & NUM2), and stores the sum in another array named RESULT

Now we will write another Assembly Program, which should add two 5-byte numbers (numbers are stored in array- NUM1 & NUM2), and stores the sum in another array named RESULT.

Let’s identify variables needed for this program.
First variables will be the one which will hold the values present in the Given Arrays and it will be NUM1 and NUM2 . Other variable will be holding the Result of Array Addition and it will be RESULT, So in all Three variables.
The identified variables are NUM1, NUM2 and RESULT.

First Line – DATA SEGMENT

DATA SEGMENT is the starting point of the Data Segment in a Program and DATA is the name given to this segment and SEGMENT is the keyword for defining Segments, Where we can declare our variables.

Next Line – NUM1 DB 36H,55H,27H,42H
NUM2 DB 38H,41H,29H,39H
RESULT DB 5 DUP (0)

NUM1 DB 36H,55H,27H,42H and NUM2 DB 38H,41H,29H,39H this line is a declaration of 8-bit Numbers Array initialized with 36H,55H,27H,42H and 38H,41H,29H,39H the numbers are seperated by Comma (,). RESULT DB 5 DUP (0) is used to Save the Result of Array Addition which will save sum of each elements of a Array NUM1 and NUM2. DUP is used to Duplicate the value in the Bracket ahead.

Next Line – DATA ENDS

DATA ENDS is the End point of the Data Segment in a Program. We can write just ENDS But to differentiate the end of which segment it is of which we have to write the same name given to the Data Segment.

Now, Selection of data type is DB data type the numbers which we are adding will be integers so DB is sufficient.

 Source code
```DATA SEGMENT
NUM1 DB 36H,55H,27H,42H
NUM2 DB 38H,41H,29H,39H
RESULT DB 5 DUP (0)
ENDS```

In Assembly programming, the variable are all defined by bytes only.

DB – Define Byte  (Size – 1 Byte)

DW – Define Word  (Size – 2 Byte)

DD – Define Double word  (Size -  4 Bytes)

DQ – Define Quad word  (Size – 8 Bytes)

DT – Define Ten Bytes  (Size – 10 Bytes)

NUMBER SYSTEM in Assembly Programming is Decimal, Octal, Hexadecimal, Binary.

In the Program, We are entering the values for the variables and Do arithmetical Operations like Addition, Subtraction, Multiplication and Division So the Computer should understand which kind of Number is entered. Hence there is a different letters for different Number Systems. O or o stands for Octal, H or h stands for Hexadecimal, B or b stands for Binary, D or d stands for Decimal. By default type of numbering system is Decimal. If you do not specify any letter then the number is understood to be Decimal (By default).

 Source code
```DATA SEGMENT
NUM1 DB 36H,55H,27H,42H
NUM2 DB 38H,41H,29H,39H
RESULT DB 5 DUP (0)
ENDS
CODE SEGMENT
ASSUME DS:DATA CS:CODE
START:
MOV AX,DATA
MOV DS,AX

LEA SI,NUM1
LEA DI,NUM2
LEA BX,RESULT

MOV CX,5
LOOP1:
MOV AL,[SI]

MOV [BX],AL

INC BX
INC SI
INC DI

LOOP LOOP1

MOV AH,4CH
INT 21H
ENDS
END START```

Explanation :

In this Assembly Language Programming, A single program is divided into four Segments which are 1. Data Segment, 2. Code Segment, 3. Stack Segment, and 4. Extra  Segment. Now, from these one is compulsory i.e. Code Segment if at all you don’t need variable(s) for your program.if you need variable(s) for your program you will need two Segments i.e. Code Segment and Data Segment.

Next Line – CODE SEGMENT

CODE SEGMENT is the starting point of the Code Segment in a Program and CODE is the name given to this segment and SEGMENT is the keyword for defining Segments, Where we can write the coding of the program.

Next Line –     ASSUME DS:DATA CS:CODE

In this Assembly Language Programming, their are Different Registers present for Different Purpose So we have to assume DATA is the name given to Data Segment register and CODE is the name given to Code Segment register (SS,ES are used in the same way as CS,DS )

Next Line – START:

START is the label used to show the starting point of the code which is written in the Code Segment. : is used to define a label as in C programming.

Next Line – MOV AX,DATA
MOV DS,AX

After Assuming DATA and CODE Segment, Still it is compulsory to initialize Data Segment to DS register.  MOV is a keyword to move the second element into the first element. But we cannot move DATA Directly to DS due to MOV commands restriction, Hence we move DATA to AX and then from AX to DS. AX is the first and most important register in the ALU unit. This part is also called INITIALIZATION OF DATA SEGMENT and It is important so that the Data elements or variables in the DATA Segment are made accessable. Other Segments are not needed to be initialized, Only assuming is enhalf.

Next Line – LEA SI,NUM1
LEA DI,NUM2
LEA BX,RESULT

LEA SI,NUM1 in this LEA stands for LOAD EFFECTIVE ADDRESS and it loads the effective address of second element into the first element.  This same code can be interchangably written as MOV DX, OFFSET PRICE where OFFSET  means effective address and MOV means move  second element into the first element. Here Base Address of variable PRICE is loaded in DX register. Similarly For LEA DI,NUM2 and LEA BX,RESULT.

Next Line – MOV CX,5

MOV CX,5 is used to move or assign value 5 ( Since the array is of length 5 ) to  CX. The program which we are wishing to write is to input eight characters from console which will be entered by the user, Hence to do so we need a loop construct. In assembly programming language we have a LOOP instruction. This works with two other helpers which are Label and Counter. The Loop start with LABEL and ends with LOOP instruction with the same LABEL name with it. the execution of the Loop depends on the value in CX register ( CX is also Called COUNTER).

Next Line – LOOP1:

LOOP1: is a LABEL and all the words ending in colon (:).

Next Line –  MOV AL,[SI]

MOV AL,[SI]  means move value in Address of SI register to AL register. [] is Refered as Value present in the Address of the Register in it.

ADD AL,[DI]  means Add value in AL register with value in Address of SI register. DAA means Decimal Adjust after Addition. e.g. 36H is present in AL register, If added with 0AH will give 40H. After DAA it will Convert to Decimal equivalent to 46H.

Next Line –  MOV [BX],AL

MOV [BX],AL  means move value in AL register to Address of BX register. [] is Refered as Value present in the Address of the Register in it.

Next Line –  INC BX
INC SI
INC DI

INC BX will increment the Address value present in BX register. Here we are using BX register as a counter and counting the numbers of Array elements to Cover all the Five elements. Similarly For INC SI and INC DI.

Next Line – LOOP LOOP1

This end of loop. In assembly programming language we have a LOOP instruction. This works with two other helpers which are Label and Counter. The Loop start with LABEL and ends with LOOP instruction with the same LABEL name with it. the execution of the Loop depends on the value in CX register ( CX is also Called COUNTER).

Next Line – MOV AH,4CH
INT 21H

The above two line code is used to exit to dos or exit to operating system. Standard Input and Standard Output related Interupts are found in INT 21H which is also called as DOS interrupt. It works with the value of AH register, If the Value is 4ch, That means Return to Operating System or DOS which is the End of the program.

Next Line – CODE ENDS

CODE ENDS is the End point of the Code Segment in a Program. We can write just ENDS But to differentiate the end of which segment it is of which we have to write the same name given to the Code Segment.

Last Line – END START

END START is the end of the label used to show the ending point of the code which is written in the Code Segment.

Note :- In this Assembly Language Programming, We have Com format and EXE format. We are Learning in EXE format only which simple then COM format to understand and Write. We can write the program in lower or upper case, But i prepare Upper Case.

Screen Shots :-

Before Execution :-

After Execution :-

Note :- To see the variable and its value you have to click vars button in the emulator.

## An Assembly program using the method of “add-and-shift” loop, in which you use the binary digits of one number to control additions of a shifted version of the other number into a running total; this is essentially the same algorithm you use when multiplying numbers by hand in decimal

Now we will write another Assembly program, Using the method of “add-and-shift” loop, in which you use the binary digits of one number to control additions of a shifted version of the other number into a running total; this is essentially the same algorithm you use when multiplying numbers by hand in decimal

Let’s identify variables needed for this program.

First variables will be the one which will hold the value predefined in the variables FIRST, SECOND to save numbers whuich are multiplied later and variable RES1 will hold PRODUCT of multiplication and Other variable RES2 will be holding the Resultant Decimal equivalent printable form to be printed for the User on Screen and Other variable will be holding the Message  “RESULT : \$”  to be printed for the User, So in all Five variables.
The identified variables are FIRST, SECOND, RES1, RES2, and MSG2.

First Line – DATA SEGMENT

DATA SEGMENT is the starting point of the Data Segment in a Program and DATA is the name given to this segment and SEGMENT is the keyword for defining Segments, Where we can declare our variables.

Next Line – FIRST DB 37
SECOND DB 25
RES1 DW ?
RES2  DB 10 DUP (‘\$’)
MSG2 DB 10,13,”RESULT : \$”

FIRST DB 37 and SECOND DB 25. We are initializing FIRST to 37 (Blank (or Nothing after number) stands for Decimal ( By Default) ),  SECOND to 25 ((Blank (or Nothing after number) stands for Decimal ( By Default) ), RES1 DW ?  We are initializing RES1 to ? (? stands for blank value), As we are accepting value from User from Console as the 4-digit number to find Sum of square of digits of it. Detailed explanation is given below. RES  DB 10 DUP (‘\$’) this line is a declaration of Array initialized with ’\$’ which works as New Line Character. \$ is used as (\n) NULL character in C program. (A Number Character is of a BYTE size Hence we have to used only DB Define Byte ) as we don’t know the lenght of the digits in the Resultant Decimal equivalent printable form, Therefore we take it approx size ten. Here 10 DUP (‘\$’) stands for N i.e. Size of Array or Array Size. DUP stands for Duplicate i.e. it will duplicate the value in All the Array with the value present in Bracket (i.e. \$). MSG2 DB 10,13,”RESULT : \$” this line is a declaration of Charater Array initialized with “RESULT : \$” and \$ is used as (\n) NULL character in C program. (A Character is of a BYTE Hence we have to use only DB Define Byte ).

Next Line – DATA ENDS

DATA ENDS is the End point of the Data Segment in a Program. We can write just ENDS But to differentiate the end of which segment it is of which we have to write the same name given to the Data Segment.

Now, Selection of data type is DB data type the numbers which we are adding will be integers so DB is sufficient.

 Source code
```DATA SEGMENT
FIRST DB 37
SECOND DB 25
RES1 DW ?
RES2  DB 10 DUP ('\$')
MSG2 DB 10,13,"RESULT : \$"
ENDS```

In Assembly programming, the variable are all defined by bytes only.

DB – Define Byte  (Size – 1 Byte)

DW – Define Word  (Size – 2 Byte)

DD – Define Double word  (Size -  4 Bytes)

DQ – Define Quad word  (Size – 8 Bytes)

DT – Define Ten Bytes  (Size – 10 Bytes)

NUMBER SYSTEM in Assembly Programming is Decimal, Octal, Hexadecimal, Binary.

In the Program, We are entering the values for the variables and Do arithmetical Operations like Addition, Subtraction, Multiplication and Division So the Computer should understand which kind of Number is entered. Hence there is a different letters for different Number Systems. O or o stands for Octal, H or h stands for Hexadecimal, B or b stands for Binary, D or d stands for Decimal. By default type of numbering system is Decimal. If you do not specify any letter then the number is understood to be Decimal (By default).

 Source code
```DATA SEGMENT
FIRST DB 37
SECOND DB 25
RES1 DW ?
RES2  DB 10 DUP ('\$')
MSG2 DB 10,13,"RESULT : \$"
ENDS
CODE SEGMENT
ASSUME DS:DATA CS:CODE
START:
MOV AX,DATA
MOV DS,AX

MOV CX,8
MOV AL,FIRST
CBW
MOV BL,SECOND

NXT:
SHR BL,1
JNC SKIP

SKIP:
SHL AX,1
LOOP NXT

MOV AX,RES1

LEA SI,RES2
CALL HEX2DEC

LEA DX,MSG2
MOV AH,9
INT 21H

LEA DX,RES2
MOV AH,9
INT 21H

MOV AH,4CH
INT 21H
CODE ENDS
HEX2DEC PROC NEAR
MOV CX,0
MOV BX,10

LOOP1: MOV DX,0
DIV BX
PUSH DX
INC CX
CMP AX,9
JG LOOP1

MOV [SI],AL

LOOP2: POP AX
INC SI
MOV [SI],AL
LOOP LOOP2
RET
HEX2DEC ENDP
END START```

Explanation :

In this Assembly Language Programming, A single program is divided into four Segments which are 1. Data Segment, 2. Code Segment, 3. Stack Segment, and 4. Extra  Segment. Now, from these one is compulsory i.e. Code Segment if at all you don’t need variable(s) for your program.if you need variable(s) for your program you will need two Segments i.e. Code Segment and Data Segment.

Next Line –CODE SEGMENT

CODE SEGMENT is the starting point of the Code Segment in a Program and CODE is the name given to this segment and SEGMENT is the keyword for defining Segments, Where we can write the coding of the program.

Next Line –     ASSUME DS:DATA CS:CODE

In this Assembly Language Programming, their are Different Registers present for Different Purpose So we have to assume DATA is the name given to Data Segment register and CODE is the name given to Code Segment register (SS,ES are used in the same way as CS,DS )

Next Line – START:

START is the label used to show the starting point of the code which is written in the Code Segment. : is used to define a label as in C programming.

Next Line – MOV AX,DATA
MOV DS,AX

After Assuming DATA and CODE Segment, Still it is compulsory to initialize Data Segment to DS register.  MOV is a keyword to move the second element into the first element. But we cannot move DATA Directly to DS due to MOV commands restriction, Hence we move DATA to AX and then from AX to DS. AX is the first and most important register in the ALU unit. This part is also called INITIALIZATION OF DATA SEGMENT and It is important so that the Data elements or variables in the DATA Segment are made accessable. Other Segments are not needed to be initialized, Only assuming is enhalf.

Next Line – MOV CX,8
MOV AL,FIRST
CBW
MOV BL,SECOND

MOV CX,8 is used to move or assign value 8 (Length of byte as we are multipling two 8-bit numbers) to  CX. In assembly programming language we have a LOOP instruction. This works with two other helpers which are Label and Counter. The Loop start with LABEL and ends with LOOP instruction with the same LABEL name with it. the execution of the Loop depends on the value in CX register ( CX is also Called COUNTER). MOV AL,FIRST means move value of Variable FIRST to AL register.  CBW means Convert byte into word, This will convert AL value to AX register. MOV BL,SECOND means move value of Variable SECONDto BL register.

Next Line – NXT:

NXT: is a LABEL and all the words ending in colon (:).

Next Line – SHR BL,1
JNC SKIP

SHR means Shift operand1 Right. The number of shifts is set by operand2. SHR BL,1  is used to Shift with 1 and JNC SKIP jump if if Carry flag is set to Zero LABEL SKIP, SKIP is the label where the compiler will JUMP. ADD RES1,AX means Adding value of AX register with variable RES1 in which value of previous addintion ( if any) is present and Finally the Product is Saved in RES1 variable.

Next Line – SKIP:

SKIP: is a LABEL and all the words ending in colon (:).

Next Line – SHL AX,1

SHL means Shift operand1 Left. The number of shifts is set by operand2. SHL AX,1  is used to Shift with 1.

Next Line – LOOP NXT

LOOP NXT This end of loop. In assembly programming language we have a LOOP instruction. This works with two other helpers which are Label and Counter. The Loop start with LABEL and ends with LOOP instruction with the same LABEL name with it. the execution of the Loop depends on the value in CX register ( CX is also Called COUNTER).

Next Line – MOV AX,RES1

MOV AX,RES1 is to move RES1 variable (Product of Multipication) to AX register. This is done due to change of AX register.

Next Line – LEA SI,RES2
CALL HEX2DEC

The above Two line code is used to initialize RES2 to SI register and Call Procedure HEX2DEC which will covert AX register value as result and Print it on user screen.

LEA SI,RES2 is used to Load Effective Address of RES2 variable to SI Register.

CALL HEX2DEC is used to Call a Procedure named HEX2DEC

Next Line – LEA DX,MSG2
MOV AH,9
INT 21H

The above two line code is used to PRINT the String or Message of the address present in DX register i.e. for MSG2.

Next Line – LEA DX,RES2
MOV AH,9
INT 21H

The above three line code is used to print String or Message present in the character Array till \$  symbol which tells the compiler to stop. As we have initialized all the values in an Array to \$ you will think what will be printed. The procedure is going to change the Array to its Resultant Decimal equivalent printable form i.e. ASCII form of a digit number.

Now, lets understand line by line

LEA DX,RES2 in this LEA stands for LOAD EFFECTIVE ADDRESS and it loads the effective address of second element into the first element.  This same code can be interchangably written as MOV DX, OFFSET RES2 where OFFSET  means effective address and MOV means move  second element into the first element.

MOV AH,9
INT 21H

The above two line code is used to PRINT the String or Message of the address present in DX register.

Standard Input and Standard Output related Interupts are found in INT 21H which is also called as DOS interrupt. It works with the value of AH register, If the Value is 9 or 9h, That means PRINT the String or Message of the address present in DX register.

Next Line – MOV AH,4CH
INT 21H

The above two line code is used to exit to dos or exit to operating system. Standard Input and Standard Output related Interupts are found in INT 21H which is also called as DOS interrupt. It works with the value of AH register, If the Value is 4ch, That means Return to Operating System or DOS which is the End of the program.

Next Line – CODE ENDS

CODE ENDS is the End point of the Code Segment in a Program. We can write just ENDS But to differentiate the end of which segment it is of which we have to write the same name given to the Code Segment.

PROCEDURE Code starts here:

Procedure is a part of code that can be called from a program in order to perform specific task.

Next Line – HEX2DEC PROC NEAR

This line of code is used to start a procedure code and we can make out the procedure by the keyword PROC which tells us the procedure is started. In assembly language we have two types of Procedures one is NEAR and other is FAR. NEAR is used to call the Procedure within the program whereas FAR is used to call the procedure outside the program. HEX2DEC is only the Name given to the Procedure Code.

Next Line –  MOV CX,0
MOV BX,10

MOV CX,0 is used to move or assign value 0 (decimal value) to  CX. The program which we are wishing to write is to covert HexaDecimal value to Decimal value, In which we will divide the number till the Quotient is going to be Zero. CX register ( CX is also Called COUNTER). CX register will count the number digit generated by dividing the Hexadecimal number by Base value of Decimal i.e.Ten. MOV BX,10 in this Base value 10 is moved to BX register, So that it is used to divide hexa number by 10.

Next Line – LOOP1: MOV DX,0

LOOP1: is a LABEL and all the words ending in colon (:) are Labels. MOV DX,0 is used to clear the unwanted value (garbage value) in DX register is removed by assigning ZERO to it. First Loop starts here.

Next Line – DIV BX

DIV instruction only works with REG or MEMORY hence we cannot use DIV 10 where 10 is immediate, So we have to move 10 to BX register (we can take any register) this we have already done above and Then DIV BX  Now DIV BX will Divide AX register with 10 which is passed to BX register and Result of division is present in AX register contains Quotientand DX register contains Remainder. Here we will not touch Quotient AX as it will be used for furture Division, But DX Remainder will be Decimal Digit and will always be less than Ten so the value will be in DL register only and to make it printable on Console (Screen) we have to add  30H So that it will become a ASCII character and will be saved in Charater Array and will be printed as String later So ADD DL,30H.

Next Line – PUSH DX
INC CX

PUSH is a stack function. Stack is an area of memory for keeping temporary data. PUSH and POP are two stack operations which stores or gets 16 bits of data. PUSH DX stores 16 bit data inside DX register into Stack Area. INC is a instruction for Increment the present in Register or Memory. INC CX will increment the value present in CX register by One. Here we are using CX register as a counter and counting the numbers of digits in their ASCII form which are pushed into Stack. So that the same count will help to POP the values out of Stack.

Next Line – MOV CX,10

MOV CX,10 is used to move or assign value 10 (decimal value) to  CX. The program which we are wishing to write is to input ten characters from console which will be entered by the user, Hence to do so we need a loop construct. In assembly programming language we have a LOOP instruction. This works with two other helpers which are Label and Counter. The Loop start with LABEL and ends with LOOP instruction with the same LABEL name with it. the execution of the Loop depends on the value in CX register ( CX is also Called COUNTER).

Next Line – CMP AX,9
JG LOOP1

CMP AX,9  is used to compare AX register with 9 and jump if AX is greater to the respective LABEL LOOP1. The result of Comparision is not stored anywhere, but flags are set according to result.  is Short Jump if first operand is Greater then second operand (as set by CMP instruction). Signed. SECOND is the label where the compiler will JUMP. First Loop ends here. Note :- this loop is without LOOP keyword and depends upon the number to be converted.

MOV [SI],AL

ADD AL,30H The Last Remainder will be Decimal Digit in AX register only as the number cannot be divided future and will always be less than Ten so the value will be in AL register only and to make it printable on Console (Screen) we have to add  30H So that it will become a ASCII character and will be saved in Charater Array and will be printed as String later. MOV [SI],AL Saving the Characters in Character Array (i.e. String) is done by Moving AL register to Address of SI register which is represented in Square Brackets i.e. [SI]. SI is assigned with the Character Array i.e. RES.

Next Line – LOOP2: POP AX
INC SI

LOOP2: is a LABEL and all the words ending in colon (:) are Labels. POP is a stack function. Stack is an area of memory for keeping temporary data. PUSH and POP are two stack operations which stores or gets 16 bits of data. POP AX gets 16 bit data to AX register from Top of Stack. INC CX will increment the value present in CX register by One. Here we are using CX register as a counter and counting the numbers of digits in their ASCII form which are pushed into Stack. So that the same count will help to POP the values out of Stack and save it in AX register. Second Loop starts here.

Next Line – MOV [SI],AL

The values out of Stack saved in AX register saved in string in this Loop. MOV [SI],AL Saving the Characters in Character Array (i.e. String) is done by Moving AL register to Address of SI register which is represented in Square Brackets i.e. [SI]. SI is assigned with the Character Array i.e. RES.

Next Line – LOOP LOOP2

This end of loop. In assembly programming language we have a LOOP instruction. This works with two other helpers which are Label and Counter. The Loop start with LABEL and ends with LOOP instruction with the same LABEL name with it. the execution of the Loop depends on the value in CX register ( CX is also Called COUNTER).

Next Line – RET

RET is a return instruction. This instruction is used only if  the control is been passed to the code outside Main like to Procedure. this return the control to the place where the Procudure was called.

Next Line – HEX2DEC ENDP

HEX2DEC ENDP is the End point of the Procedure in a Program.

This line of code is used to end the procedure code and we can make out the procedure by the keyword ENDP which tells us the procedure is ended. In assembly language we have two types of Procedures one is NEAR and other is FAR. NEAR is used to call the Procedure within the program whereas FAR is used to call the procedure outside the program. HEX2DEC is only the Name given to the Procedure Code.

Last Line – END START

END START is the end of the label used to show the ending point of the code which is written in the Code Segment.

Note :- In this Assembly Language Programming, We have Com format and EXE format. We are Learning in EXE format only which simple then COM format to understand and Write. We can write the program in lower or upper case, But i prepare Upper Case.

Screen Shots :-

Variables Before Execution :-

Variables After Execution :-

Output :-

Note :- To see the variable and its value you have to click vars button in the emulator.

## An Assembly program, which takes the input of 4-digit number, and display the sum of square of digits

Now we will write another Assembly program, which takes the input of  4-digit number, and display the sum of square of digits

Let’s identify variables needed for this program.

First variables will be the one which will hold the value entered by user in the variables D1, D2, D3, D4 to save 4-Digits separately in 4 variables  and variable SUM will hold sum of square of digits  and Other variable RES will be holding the Resultant Decimal equivalent printable form to be printed for the User on Screen and Other variables will be holding the Messages “ENTER NUMBER WITH FOUR DIGITS : \$” and “RESULT : \$”  to be printed for the User, So in all Eight variables.
The identified variables are D1, D2, D3, D4SUM, RES, MSG1, and MSG2.

First Line – DATA SEGMENT

DATA SEGMENT is the starting point of the Data Segment in a Program and DATA is the name given to this segment and SEGMENT is the keyword for defining Segments, Where we can declare our variables.

Next Line – MSG1 DB “ENTER NUMBER WITH FOUR DIGITS : \$”
MSG2 DB 10,13,”RESULT : \$”
D1 DB ?
D2 DB ?
D3 DB ?
D4 DB ?
SUM DB ?
RES  DB 10 DUP (‘\$’)

D1 DB ?, D2 DB ?, D3 DB ?, D4 DB ?, SUM DB ?  We are initializing ALL to ? (? stands for blank value), As we are accepting value from User from Console as the 4-digit number to find Sum of square of digits of it. Detailed explanation is given below. RES  DB 10 DUP (‘\$’) this line is a declaration of Array initialized with ’\$’ which works as New Line Character. \$ is used as (\n) NULL character in C program. (A Number Character is of a BYTE size Hence we have to used only DB Define Byte ) as we don’t know the lenght of the digits in the Resultant Decimal equivalent printable form, Therefore we take it approx size ten. Here 10 DUP (‘\$’) stands for N i.e. Size of Array or Array Size. DUP stands for Duplicate i.e. it will duplicate the value in All the Array with the value present in Bracket (i.e. \$). MSG1 DB “ENTER NUMBER WITH FOUR DIGITS : \$” this line is a declaration of Charater Array initialized with “ENTER NUMBER WITH FOUR DIGITS : \$” and \$ is used as (\n) NULL character in C program. (A Character is of a BYTE Hence we have to use only DB Define Byte ). MSG2 DB 10,13,”RESULT : \$”

Next Line – DATA ENDS

DATA ENDS is the End point of the Data Segment in a Program. We can write just ENDS But to differentiate the end of which segment it is of which we have to write the same name given to the Data Segment.

Now, Selection of data type is DB data type the numbers which we are adding will be integers so DB is sufficient.

 Source code
```DATA SEGMENT
MSG1 DB "ENTER NUMBER WITH FOUR DIGITS : \$"
MSG2 DB 10,13,"RESULT : \$"
D1 DB ?
D2 DB ?
D3 DB ?
D4 DB ?
SUM DB ?
RES  DB 10 DUP ('\$')
DATA ENDS```

In Assembly programming, the variable are all defined by bytes only.

DB – Define Byte  (Size – 1 Byte)

DW – Define Word  (Size – 2 Byte)

DD – Define Double word  (Size -  4 Bytes)

DQ – Define Quad word  (Size – 8 Bytes)

DT – Define Ten Bytes  (Size – 10 Bytes)

NUMBER SYSTEM in Assembly Programming is Decimal, Octal, Hexadecimal, Binary.

In the Program, We are entering the values for the variables and Do arithmetical Operations like Addition, Subtraction, Multiplication and Division So the Computer should understand which kind of Number is entered. Hence there is a different letters for different Number Systems. O or o stands for Octal, H or h stands for Hexadecimal, B or b stands for Binary, D or d stands for Decimal. By default type of numbering system is Decimal. If you do not specify any letter then the number is understood to be Decimal (By default).

 Source code
```DATA SEGMENT
MSG1 DB "ENTER NUMBER WITH FOUR DIGITS : \$"
MSG2 DB 10,13,"RESULT : \$"
D1 DB ?
D2 DB ?
D3 DB ?
D4 DB ?
SUM DB ?
RES  DB 10 DUP ('\$')
DATA ENDS
CODE SEGMENT
ASSUME DS:DATA CS:CODE
START:
MOV AX,DATA
MOV DS,AX

LEA DX,MSG1
MOV AH,9
INT 21H

MOV AH,1
INT 21H
SUB AL,30H
MOV AH,0
MUL AL
MOV D1,AL

MOV AH,1
INT 21H
SUB AL,30H
MOV AH,0
MUL AL
MOV D2,AL

MOV AH,1
INT 21H
SUB AL,30H
MOV AH,0
MUL AL
MOV D3,AL

MOV AH,1
INT 21H
SUB AL,30H
MOV AH,0
MUL AL
MOV D4,AL

MOV SUM,AL

LEA SI,RES
CALL HEX2DEC

LEA DX,MSG2
MOV AH,9
INT 21H

LEA DX,RES
MOV AH,9
INT 21H

MOV AH,4CH
INT 21H
CODE ENDS
HEX2DEC PROC NEAR
MOV CX,0
MOV BX,10

LOOP1: MOV DX,0
DIV BX
PUSH DX
INC CX
CMP AX,9
JG LOOP1

MOV [SI],AL

LOOP2: POP AX
INC SI
MOV [SI],AL
LOOP LOOP2
RET
HEX2DEC ENDP
END START```

Explanation :

In this Assembly Language Programming, A single program is divided into four Segments which are 1. Data Segment, 2. Code Segment, 3. Stack Segment, and 4. Extra  Segment. Now, from these one is compulsory i.e. Code Segment if at all you don’t need variable(s) for your program.if you need variable(s) for your program you will need two Segments i.e. Code Segment and Data Segment.

Next Line –CODE SEGMENT

CODE SEGMENT is the starting point of the Code Segment in a Program and CODE is the name given to this segment and SEGMENT is the keyword for defining Segments, Where we can write the coding of the program.

Next Line –     ASSUME DS:DATA CS:CODE

In this Assembly Language Programming, their are Different Registers present for Different Purpose So we have to assume DATA is the name given to Data Segment register and CODE is the name given to Code Segment register (SS,ES are used in the same way as CS,DS )

Next Line – START:

START is the label used to show the starting point of the code which is written in the Code Segment. : is used to define a label as in C programming.

Next Line – MOV AX,DATA
MOV DS,AX

After Assuming DATA and CODE Segment, Still it is compulsory to initialize Data Segment to DS register.  MOV is a keyword to move the second element into the first element. But we cannot move DATA Directly to DS due to MOV commands restriction, Hence we move DATA to AX and then from AX to DS. AX is the first and most important register in the ALU unit. This part is also called INITIALIZATION OF DATA SEGMENT and It is important so that the Data elements or variables in the DATA Segment are made accessable. Other Segments are not needed to be initialized, Only assuming is enhalf.

Next Line – LEA DX,MSG1
MOV AH,9
INT 21H

The above three line code is used to print String or Message present in the character Array till \$  symbol which tells the compiler to stop.

Now, lets understand line by line

LEA DX,MSG1 in this LEA stands for LOAD EFFECTIVE ADDRESS and it loads the effective address of second element into the first element.  This same code can be interchangably written as MOV DX, OFFSET MSG1 where OFFSET  means effective address and MOV means move  second element into the first element.

MOV AH,9
INT 21H

The above two line code is used to PRINT the String or Message of the address present in DX register.

Standard Input and Standard Output related Interupts are found in INT 21H which is also called as DOS interrupt. It works with the value of AH register, If the Value is 9 or 9h, That means PRINT the String or Message of the address present in DX register.

Next Line – MOV AH,1
INT 21H

The above three line code is used to Read a Character from Console and save the value entered in variable R in its ASCII form.

Standard Input and Standard Output related Interupts are found in INT 21H which is also called as DOS interrupt. It works with the value of AH register, If the Value is 1 or 1h, That means READ a Character from Console, Echo it on screen and save the value entered in AL register.

Next Line – SUB AL,30H
MOV AH,0
MUL AL
MOV D1,AL

The above Two line code is used to convert the value entered in variable R from ASCII form to its BCD form. This can be done by subtracting 30H i.e. SUB AL,30H. The value coming from Console is Basically in ASCII form. eg. When you enter 5 we see 35H,So by subtracting 30H we get back to value as 5. SUB AL,30H means subtracting 30H from AL. MOV AH,0 is used to clear the unwanted value (garbage value) in AH register is removed by assigning ZERO to it. MUL AL is used to Multiply AL with AX register  i.e.Value present in AX register. MOV D1,AL  means move value in AL register into variable D1.

Similarly

Next Line – MOV AH,1
INT 21H
SUB AL,30H
MOV AH,0
MUL AL
MOV D2,AL

MOV AH,1
INT 21H
SUB AL,30H
MOV AH,0
MUL AL
MOV D3,AL

MOV AH,1
INT 21H
SUB AL,30H
MOV AH,0
MUL AL
MOV D4,AL

Same as above to scan 4-digit number separately multiply it with itself to get Square and save it in D1,D2,D3,D4 separately and from the Console (Screen) entered by User.

MOV SUM,AL

ADD AL,D3 means Adding value of variable D3 from AL register in which value of variable D4 is present. ADD AL,D2 means Adding value of variable D2 from AL register. ADD AL,D1 means Adding value of variable D2 from AL register. MOV SUM,AL  means move value in AL register into variable SUM.

Next Line – LEA SI,RES
CALL HEX2DEC

The above Two line code is used to initialize RES to SI register and Call Procedure HEX2DEC which will covert AX register value as result and Print it on user screen.

LEA SI,RES is used to Load Effective Address of RES variable to SI Register.

CALL HEX2DEC is used to Call a Procedure named HEX2DEC

Next Line – LEA DX,MSG2
MOV AH,9
INT 21H

The above two line code is used to PRINT the String or Message of the address present in DX register i.e. for MSG2.

Next Line – LEA DX,RES
MOV AH,9
INT 21H

The above three line code is used to print String or Message present in the character Array till \$  symbol which tells the compiler to stop. As we have initialized all the values in an Array to \$ you will think what will be printed. The procedure is going to change the Array to its Resultant Decimal equivalent printable form i.e. ASCII form of a digit number.

Now, lets understand line by line

LEA DX,RES in this LEA stands for LOAD EFFECTIVE ADDRESS and it loads the effective address of second element into the first element.  This same code can be interchangably written as MOV DX, OFFSET RES where OFFSET  means effective address and MOV means move  second element into the first element.

MOV AH,9
INT 21H

The above two line code is used to PRINT the String or Message of the address present in DX register.

Standard Input and Standard Output related Interupts are found in INT 21H which is also called as DOS interrupt. It works with the value of AH register, If the Value is 9 or 9h, That means PRINT the String or Message of the address present in DX register.

Next Line – MOV AH,4CH
INT 21H

The above two line code is used to exit to dos or exit to operating system. Standard Input and Standard Output related Interupts are found in INT 21H which is also called as DOS interrupt. It works with the value of AH register, If the Value is 4ch, That means Return to Operating System or DOS which is the End of the program.

Next Line – CODE ENDS

CODE ENDS is the End point of the Code Segment in a Program. We can write just ENDS But to differentiate the end of which segment it is of which we have to write the same name given to the Code Segment.

PROCEDURE Code starts here:

Procedure is a part of code that can be called from a program in order to perform specific task.

Next Line – HEX2DEC PROC NEAR

This line of code is used to start a procedure code and we can make out the procedure by the keyword PROC which tells us the procedure is started. In assembly language we have two types of Procedures one is NEAR and other is FAR. NEAR is used to call the Procedure within the program whereas FAR is used to call the procedure outside the program. HEX2DEC is only the Name given to the Procedure Code.

Next Line –  MOV CX,0
MOV BX,10

MOV CX,0 is used to move or assign value 0 (decimal value) to  CX. The program which we are wishing to write is to covert HexaDecimal value to Decimal value, In which we will divide the number till the Quotient is going to be Zero. CX register ( CX is also Called COUNTER). CX register will count the number digit generated by dividing the Hexadecimal number by Base value of Decimal i.e.Ten. MOV BX,10 in this Base value 10 is moved to BX register, So that it is used to divide hexa number by 10.

Next Line – LOOP1: MOV DX,0

LOOP1: is a LABEL and all the words ending in colon (:) are Labels. MOV DX,0 is used to clear the unwanted value (garbage value) in DX register is removed by assigning ZERO to it. First Loop starts here.

Next Line – DIV BX

DIV instruction only works with REG or MEMORY hence we cannot use DIV 10 where 10 is immediate, So we have to move 10 to BX register (we can take any register) this we have already done above and Then DIV BX  Now DIV BX will Divide AX register with 10 which is passed to BX register and Result of division is present in AX register contains Quotientand DX register contains Remainder. Here we will not touch Quotient AX as it will be used for furture Division, But DX Remainder will be Decimal Digit and will always be less than Ten so the value will be in DL register only and to make it printable on Console (Screen) we have to add  30H So that it will become a ASCII character and will be saved in Charater Array and will be printed as String later So ADD DL,30H.

Next Line – PUSH DX
INC CX

PUSH is a stack function. Stack is an area of memory for keeping temporary data. PUSH and POP are two stack operations which stores or gets 16 bits of data. PUSH DX stores 16 bit data inside DX register into Stack Area. INC is a instruction for Increment the present in Register or Memory. INC CX will increment the value present in CX register by One. Here we are using CX register as a counter and counting the numbers of digits in their ASCII form which are pushed into Stack. So that the same count will help to POP the values out of Stack.

Next Line – MOV CX,10

MOV CX,10 is used to move or assign value 10 (decimal value) to  CX. The program which we are wishing to write is to input ten characters from console which will be entered by the user, Hence to do so we need a loop construct. In assembly programming language we have a LOOP instruction. This works with two other helpers which are Label and Counter. The Loop start with LABEL and ends with LOOP instruction with the same LABEL name with it. the execution of the Loop depends on the value in CX register ( CX is also Called COUNTER).

Next Line – CMP AX,9
JG LOOP1

CMP AX,9  is used to compare AX register with 9 and jump if AX is greater to the respective LABEL LOOP1. The result of Comparision is not stored anywhere, but flags are set according to result.  is Short Jump if first operand is Greater then second operand (as set by CMP instruction). Signed. SECOND is the label where the compiler will JUMP. First Loop ends here. Note :- this loop is without LOOP keyword and depends upon the number to be converted.

MOV [SI],AL

ADD AL,30H The Last Remainder will be Decimal Digit in AX register only as the number cannot be divided future and will always be less than Ten so the value will be in AL register only and to make it printable on Console (Screen) we have to add  30H So that it will become a ASCII character and will be saved in Charater Array and will be printed as String later. MOV [SI],AL Saving the Characters in Character Array (i.e. String) is done by Moving AL register to Address of SI register which is represented in Square Brackets i.e. [SI]. SI is assigned with the Character Array i.e. RES.

Next Line – LOOP2: POP AX
INC SI

LOOP2: is a LABEL and all the words ending in colon (:) are Labels. POP is a stack function. Stack is an area of memory for keeping temporary data. PUSH and POP are two stack operations which stores or gets 16 bits of data. POP AX gets 16 bit data to AX register from Top of Stack. INC CX will increment the value present in CX register by One. Here we are using CX register as a counter and counting the numbers of digits in their ASCII form which are pushed into Stack. So that the same count will help to POP the values out of Stack and save it in AX register. Second Loop starts here.

Next Line – MOV [SI],AL

The values out of Stack saved in AX register saved in string in this Loop. MOV [SI],AL Saving the Characters in Character Array (i.e. String) is done by Moving AL register to Address of SI register which is represented in Square Brackets i.e. [SI]. SI is assigned with the Character Array i.e. RES.

Next Line – LOOP LOOP2

This end of loop. In assembly programming language we have a LOOP instruction. This works with two other helpers which are Label and Counter. The Loop start with LABEL and ends with LOOP instruction with the same LABEL name with it. the execution of the Loop depends on the value in CX register ( CX is also Called COUNTER).

Next Line – RET

RET is a return instruction. This instruction is used only if  the control is been passed to the code outside Main like to Procedure. this return the control to the place where the Procudure was called.

Next Line – HEX2DEC ENDP

HEX2DEC ENDP is the End point of the Procedure in a Program.

This line of code is used to end the procedure code and we can make out the procedure by the keyword ENDP which tells us the procedure is ended. In assembly language we have two types of Procedures one is NEAR and other is FAR. NEAR is used to call the Procedure within the program whereas FAR is used to call the procedure outside the program. HEX2DEC is only the Name given to the Procedure Code.

Last Line – END START

END START is the end of the label used to show the ending point of the code which is written in the Code Segment.

Note :- In this Assembly Language Programming, We have Com format and EXE format. We are Learning in EXE format only which simple then COM format to understand and Write. We can write the program in lower or upper case, But i prepare Upper Case.

Screen Shots :-

Output :-

Note :- To see the variable and its value you have to click vars button in the emulator.

## An Assembly Language program two subroutines encrypting and decrypting – IGNOU MCA Assignment 2013

MASTER OF COMPUTER APPLICATIONS
Course Code : MCSL-017
Course Title : C and Assembly Language Programming
Assignment Number : MCA(1)/L017/Assign/2013

Write a Program in assembly language that has two subroutines: One for encrypting alphabets of a string and second for decrypting the encoded string. In Encryption, simply convert a character /number into its predefined numerical/character value. Decryption is a reverse process of encryption. Write suitable Main program in C that calls these function. Test your program suitably

DATA SEGMENT
MSG1 DB 10,13,’ENTER STRING HERE :- \$’
MSG2 DB 10,13,’ENCRYPTED STRING IS :- \$’
MSG3 DB 10,13,’DECRYPTED STRING IS : \$’

P1 LABEL BYTE
M1 DB 0FFH
L1 DB ?
P11 DB 0FFH DUP (‘\$’)

DATA ENDS

DISPLAY MACRO MSG
MOV AH,9
LEA DX,MSG
INT 21H
ENDM
CODE SEGMENT
ASSUME CS:CODE,DS:DATA
START:
MOV AX,DATA
MOV DS,AX

DISPLAY MSG1

LEA DX,P1
MOV AH,0AH
INT 21H

LEA SI,P11
MOV CL,L1
CALL ENCRYPT

DISPLAY MSG2
DISPLAY P11

LEA SI,P11
MOV CL,L1
CALL ENCRYPT

DISPLAY MSG3
DISPLAY P11

MOV AH,4CH
INT 21H
CODE ENDS

ENCRYPT PROC NEAR
MOV CH,0
CHECK1:
CMP [SI],2FH
JB DONE1
CMP [SI],3AH
JB NUM1

CMP [SI],41H
JB DONE1
CMP [SI],5BH
JB UPR1

CMP [SI],61H
JB DONE1
CMP [SI],7BH
JB LWR1

NUM1:    CMP [SI],35H
JB LNUM1
SUB [SI],05H
JMP DONE1
LNUM1:
JMP DONE1

UPR1:    CMP [SI],4EH
JB LUPR1
SUB [SI],0DH
JMP DONE1
LUPR1:
JMP DONE1

LWR1:    CMP [SI],6EH
JB LLWR1
SUB [SI],0DH
JMP DONE1
LLWR1:

DONE1:
INC SI
LOOP CHECK1
RET
ENCRYPT ENDP

DECRYPT PROC NEAR
MOV CH,0
CHECK2:
CMP [SI],2FH
JB DONE2
CMP [SI],3AH
JB NUM2

CMP [SI],41H
JB DONE2
CMP [SI],5BH
JB UPR2

CMP [SI],61H
JB DONE2
CMP [SI],7BH
JB LWR2

NUM2:   CMP [SI],35H
JB LNUM2
JMP DONE2
LNUM2:
SUB [SI],05H
JMP DONE2

UPR2:    CMP [SI],4EH
JB LUPR2
JMP DONE2
LUPR2:
SUB [SI],0DH
JMP DONE2

LWR2:    CMP [SI],6EH
JB LLWR2
JMP DONE2
LLWR2:
SUB [SI],0DH

DONE2:
INC SI
LOOP CHECK2
RET
DECRYPT ENDP

END START

program code :

 Source code
` DATA SEGMENT    MSG1 DB 10,13,'ENTER STRING HERE :- \$'       MSG2 DB 10,13,'ENCRYPTED STRING IS :- \$'    MSG3 DB 10,13,'DECRYPTED STRING IS : \$'       P1 LABEL BYTE    M1 DB 0FFH    L1 DB ?    P11 DB 0FFH DUP ('\$')   DATA ENDSDISPLAY MACRO MSG    MOV AH,9    LEA DX,MSG    INT 21HENDM   CODE SEGMENT    ASSUME CS:CODE,DS:DATASTART:        MOV AX,DATA        MOV DS,AX                                       DISPLAY MSG1               LEA DX,P1        MOV AH,0AH            INT 21H                              LEA SI,P11        MOV CL,L1        CALL ENCRYPT               DISPLAY MSG2        DISPLAY P11                                       LEA SI,P11        MOV CL,L1        CALL ENCRYPT               DISPLAY MSG3        DISPLAY P11               MOV AH,4CH        INT 21HCODE ENDSENCRYPT PROC NEAR        MOV CH,0       CHECK1:        CMP [SI],2FH        JB DONE1        CMP [SI],3AH        JB NUM1               CMP [SI],41H        JB DONE1        CMP [SI],5BH        JB UPR1               CMP [SI],61H        JB DONE1        CMP [SI],7BH        JB LWR1       NUM1:    CMP [SI],35H        JB LNUM1        SUB [SI],05H        JMP DONE1   LNUM1:            ADD [SI],05H        JMP DONE1          UPR1:    CMP [SI],4EH        JB LUPR1        SUB [SI],0DH        JMP DONE1   LUPR1:            ADD [SI],0DH        JMP DONE1LWR1:    CMP [SI],6EH        JB LLWR1        SUB [SI],0DH        JMP DONE1   LLWR1:            ADD [SI],0DH             DONE1:               INC SI        LOOP CHECK1       RETENCRYPT ENDPDECRYPT PROC NEAR        MOV CH,0       CHECK2:        CMP [SI],2FH        JB DONE2        CMP [SI],3AH        JB NUM2               CMP [SI],41H        JB DONE2        CMP [SI],5BH        JB UPR2               CMP [SI],61H        JB DONE2        CMP [SI],7BH        JB LWR2       NUM2:   CMP [SI],35H        JB LNUM2        ADD [SI],05H        JMP DONE2   LNUM2:            SUB [SI],05H        JMP DONE2          UPR2:    CMP [SI],4EH        JB LUPR2        ADD [SI],0DH        JMP DONE2   LUPR2:            SUB [SI],0DH        JMP DONE2LWR2:    CMP [SI],6EH        JB LLWR2        ADD [SI],0DH        JMP DONE2   LLWR2:            SUB [SI],0DH             DONE2:               INC SI        LOOP CHECK2       RETDECRYPT ENDP   END START`

Screen shots :-

Output :-

## An assembly program to accept a decimal number and print it’s 2′s complement binary and hexadecimal – IGNOU MCA Assignment 2013

MASTER OF COMPUTER APPLICATIONS
Course Code : MCSL-017
Course Title : C and Assembly Language Programming
Assignment Number : MCA(1)/L017/Assign/2013

Write an assembly language program to accept a decimal number and display it’s two’s complement representation in binary and hexadecimal formats

DATA SEGMENT
DIGIT1 DB ?
DIGIT2 DB ?
HEXNUM DB ?
TWOSCOMP DB 10 DUP (‘\$’)
MSG1 DB “ENTER NUMBER : \$”
MSG2 DB 10,13,”HEXADECIMAL FORM IS : \$”
MSG3 DB 10,13,”TWO’S COMPLEMENT FORM IS : \$”
DATA ENDS

CODE SEGMENT
ASSUME DS:DATA,CS:CODE
START:
MOV AX,DATA
MOV DS,AX

LEA DX,MSG1
MOV AH,9
INT 21H

MOV AH,1
INT 21H
SUB AL,30H
MOV DIGIT1,AL

MOV AH,1
INT 21H
SUB AL,30H
MOV DIGIT2,AL

MOV AH,0
MOV AL,DIGIT1

MOV CL,10
MUL CL

MOV HEXNUM,AL

NOT AL

LEA SI,TWOSCOMP
CALL HEX2BIN

MOV AL,HEXNUM
MOV BL,AL
AND AL,0F0H
AND BL,0FH

MOV CL,04H
ROL AL,CL

MOV [DI],AL
MOV [DI+1],BL

MOV CL,2
MOV CH,0
CHECK:
CMP [SI],9
JG ALPHA

JMP DONE

DONE:
INC SI
LOOP CHECK

LEA DX,MSG2
MOV AH,9
INT 21H

MOV AH,9
INT 21H

LEA DX,MSG3
MOV AH,9
INT 21H

LEA DX,TWOSCOMP
MOV AH,9
INT 21H

MOV AH,4CH
INT 21H
CODE ENDS

HEX2BIN PROC NEAR
MOV CX,0
MOV BX,2

LOOP1: MOV DX,0
DIV BX
PUSH DX
INC CX
CMP AX,1
JG LOOP1

MOV [SI],AL

LOOP2: POP AX
INC SI
MOV [SI],AL
LOOP LOOP2
RET
HEX2BIN ENDP

END START

program code :

 Source code
`DATA SEGMENT    DIGIT1 DB ?    DIGIT2 DB ?    HEXNUM DB ?    HEXADEC DB 3 DUP ('\$')    TWOSCOMP DB 10 DUP ('\$')    MSG1 DB "ENTER NUMBER : \$"    MSG2 DB 10,13,"HEXADECIMAL FORM IS : \$"    MSG3 DB 10,13,"TWO'S COMPLEMENT FORM IS : \$"DATA ENDSCODE SEGMENT        ASSUME DS:DATA,CS:CODESTART:           MOV AX,DATA    MOV DS,AX       LEA DX,MSG1    MOV AH,9    INT 21H       MOV AH,1    INT 21H    SUB AL,30H    MOV DIGIT1,AL       MOV AH,1    INT 21H    SUB AL,30H    MOV DIGIT2,AL       MOV AH,0    MOV AL,DIGIT1       MOV CL,10    MUL CL       ADD AL,DIGIT2    MOV HEXNUM,AL       NOT AL    ADD AL,1    LEA SI,TWOSCOMP    CALL HEX2BIN       MOV AL,HEXNUM    MOV BL,AL    AND AL,0F0H    AND BL,0FH         MOV CL,04H    ROL AL,CL         LEA DI,HEXADEC    MOV [DI],AL    MOV [DI+1],BL          LEA SI,HEXADEC               MOV CL,2       MOV CH,0       CHECK:       CMP [SI],9       JG ALPHA   NUM:   ADD [SI],30H       JMP DONE      ALPHA: ADD [SI],37H             DONE:              INC SI       LOOP CHECK             LEA DX,MSG2    MOV AH,9    INT 21H          LEA DX,HEXADEC    MOV AH,9    INT 21H       LEA DX,MSG3    MOV AH,9    INT 21H          LEA DX,TWOSCOMP    MOV AH,9    INT 21H                MOV AH,4CH    INT 21H        CODE ENDS  HEX2BIN PROC NEAR    MOV CX,0    MOV BX,2   LOOP1: MOV DX,0       DIV BX       ADD DL,30H       PUSH DX       INC CX       CMP AX,1       JG LOOP1            ADD AL,30H       MOV [SI],AL     LOOP2: POP AX       INC SI       MOV [SI],AL       LOOP LOOP2       RETHEX2BIN ENDP              END START`

Screen shots :-

Outputs :-

## An Assembly Language program to convert packed BCD to equivalent binary – IGNOU MCA Assignment 2013

BACHELOR  OF COMPUTER APPLICATIONS
Course Code : BCSL-022
Course Title : Assembly Language Programming Lab
Assignment Number : BCA(II)/BCSL022/Assign/13

Write and run an assembly language program that converts a packed two digit BCD number in AL register to equivalent binary number. The binary number is stored in the AH register

DATA SEGMENT
PACKEDBCD DB 52H
BINARY    DB ?
DATA ENDS
CODE SEGMENT
ASSUME DS:DATA CS:CODE
START:
MOV AX,DATA
MOV DS,AX

MOV AH,0
MOV AL,PACKEDBCD
MOV BL,AL

AND AL,0F0H
AND BL,0FH

MOV CL,04H
ROL AL,CL

MOV CL,10
MUL CL

MOV AH,AL
MOV BINARY,AH

MOV AH,4CH
INT 21H
CODE ENDS
END START

program code :

 Source code
`DATA SEGMENT     PACKEDBCD DB 52H     BINARY    DB ?DATA ENDSCODE SEGMENT    ASSUME DS:DATA CS:CODESTART:      MOV AX,DATA      MOV DS,AX          MOV AH,0      MOV AL,PACKEDBCD      MOV BL,AL           AND AL,0F0H      AND BL,0FH           MOV CL,04H      ROL AL,CL           MOV CL,10      MUL CL           ADD AL,BL           MOV AH,AL      MOV BINARY,AH                    MOV AH,4CH      INT 21H    CODE ENDSEND START`

Screen shots :-

Before Execution :-

After Execution :-

## A near procedure assembly Language program to convert ASCII to binary – IGNOU MCA Assignment 2013

BACHELOR  OF COMPUTER APPLICATIONS
Course Code : BCSL-022
Course Title : Assembly Language Programming Lab
Assignment Number : BCA(II)/BCSL022/Assign/13

Write and run (using appropriate calling program) a near procedure in assembly language that converts an ASCII digit passed to it on AL register to equivalent binary value. The value is returned back on the AL register itself

DATA SEGMENT
STR1 DB “MAHESH\$”
STR2 DB 7 DUP (‘\$’)
MSG1 DB 10,13,’STORED STRING IN MEMORY IS : \$’
MSG2 DB 10,13,’REVERSE STRING IS : \$’
DATA ENDS

DISPLAY MACRO MSG
MOV AH,9
LEA DX,MSG
INT 21H
ENDM
CODE SEGMENT
ASSUME CS:CODE,DS:DATA
START:
MOV AX,DATA
MOV DS,AX

DISPLAY MSG1

DISPLAY STR1

LEA SI,STR2
LEA DI,STR1

MOV CX,6
REVERSE:
MOV AL,[DI]
MOV [SI],AL
INC SI
DEC DI
LOOP REVERSE

DISPLAY MSG2

DISPLAY STR2

MOV AH,4CH
INT 21H
CODE ENDS
END START

program code :

 Source code
`DATA SEGMENT    STR1 DB "MAHESH\$"    STR2 DB 7 DUP ('\$')    MSG1 DB 10,13,'STORED STRING IN MEMORY IS : \$'    MSG2 DB 10,13,'REVERSE STRING IS : \$'DATA ENDSDISPLAY MACRO MSG    MOV AH,9    LEA DX,MSG    INT 21HENDM   CODE SEGMENT    ASSUME CS:CODE,DS:DATASTART:        MOV AX,DATA        MOV DS,AX                                       DISPLAY MSG1                            DISPLAY STR1                               LEA SI,STR2        LEA DI,STR1        ADD DI,5                       MOV CX,6REVERSE:        MOV AL,[DI]        MOV [SI],AL        INC SI        DEC DI        LOOP REVERSE               DISPLAY MSG2                           DISPLAY STR2                             MOV AH,4CH        INT 21HCODE ENDSEND START`

Screen shots :-

Output :-

## An Assembly Language program to reverse a string in memory and displayed – IGNOU MCA Assignment 2013

BACHELOR  OF COMPUTER APPLICATIONS
Course Code : BCSL-022
Course Title : Assembly Language Programming Lab
Assignment Number : BCA(II)/BCSL022/Assign/13

Write and run an Assembly language program that reverses a string. You may assume that the string is available in the memory and is 6 byte long. The reversed string should be stored in separate memory locations and should be displayed

DATA SEGMENT
STR1 DB “MAHESH\$”
STR2 DB 7 DUP (‘\$’)
MSG1 DB 10,13,’STORED STRING IN MEMORY IS : \$’
MSG2 DB 10,13,’REVERSE STRING IS : \$’
DATA ENDS

DISPLAY MACRO MSG
MOV AH,9
LEA DX,MSG
INT 21H
ENDM
CODE SEGMENT
ASSUME CS:CODE,DS:DATA
START:
MOV AX,DATA
MOV DS,AX

DISPLAY MSG1

DISPLAY STR1

LEA SI,STR2
LEA DI,STR1

MOV CX,6
REVERSE:
MOV AL,[DI]
MOV [SI],AL
INC SI
DEC DI
LOOP REVERSE

DISPLAY MSG2

DISPLAY STR2

MOV AH,4CH
INT 21H
CODE ENDS
END START

program code :

 Source code
`DATA SEGMENT    STR1 DB "MAHESH\$"    STR2 DB 7 DUP ('\$')    MSG1 DB 10,13,'STORED STRING IN MEMORY IS : \$'    MSG2 DB 10,13,'REVERSE STRING IS : \$'DATA ENDSDISPLAY MACRO MSG    MOV AH,9    LEA DX,MSG    INT 21HENDM   CODE SEGMENT    ASSUME CS:CODE,DS:DATASTART:        MOV AX,DATA        MOV DS,AX                                       DISPLAY MSG1                            DISPLAY STR1                               LEA SI,STR2        LEA DI,STR1        ADD DI,5                       MOV CX,6REVERSE:        MOV AL,[DI]        MOV [SI],AL        INC SI        DEC DI        LOOP REVERSE               DISPLAY MSG2                           DISPLAY STR2                             MOV AH,4CH        INT 21HCODE ENDSEND START`

Screen shots :-

Output :-